Tires

[Marcus2000monster]

What size tires would y’all get? I have 17 inch stock wheels. I would like to have lower rpms if I can and I would like to get better fuel mileage. Suggestions?

[Mopar1973Man]

More about weight and contact. Lighter the wheel and tire assembly means better MPG's. RPM's should be setup at 2k when at highway speed. Larger tires can reduce RPM's at a cost of rotational mass and more wear on front suspension and brakes. I went the opposite direct to the 235/85 R16 cut 23-25 pounds of rotational mass and gain a few MPG's becuase the RPM's are right around 1,900 at 65 MPH at 80 MPH I'm about 2,400 RPM but this is just wasteful. Optimal speed on my truck is 55 MPH which still pushes upwards of 20+ MPG. Just think about racing slicks you can get those and they barely weigh 23-27 pounds for a rear tire there is no rotational mass. All these wide tire tires exceed 100 pounds once you toss the wide wheels in. My old aluminum mags and a 235's I could weigh in at 62 pounds per tire and wheel. This means more power to the ground and less wasted in spinning heavy wheels. Best way to show this go to the park...

 

 

Remember these as a kid. The smaller ones a couple a kids could get spinning rather good. Now the larger ones took even more kids to get spinning a good fast rate. Then when it can to stopping because of the kids hanging off then it took even more kids to stop the wheel if it was larger smaller ones stopped rather easy. Just consider your tire size the same way. 

 

I worked with a local guy that wanted 37" tire. He's now very happy because we had both axles re-gear properly to match the RPM's for his driving style. He also did all the supporting mods to the front suspension. It can be done but its not as easy as bolting on a set of new wheels with wide tires there is a lot to consider and be aware of...

[Dieselfuture]

I'm running 285/70/17 and I think it's a good size all around. Sure my probably losing few mpgs but don't like pizza cutters look. Anything bigger and front end is going to fall up part quicker. I almost bought 285/75/17 because it was considered extreme size in toyos and they had side tread too, looked cool but I'm glad I didn't. Plus I'm having crap luck with these toyos. Be something else next time. 

[Marcus2000monster]

Mpg matters a lot too me but I also don’t want skinny dumb looking tires lol

 

[Mopar1973Man]

Little something to consider about tire sizes. Just get out of your truck and start walking in the deep snow. What happens you sink to the bottom right. If you put on snowshoes you can walk on top of the snow. This points out the fact why you should run narrow tires in the winter because you gain more traction because of the contact patch being smaller giving more pounds per square inch of tire contact. Wider and larger the contact patch the worse off you end up in winter road conditions. Maybe that's why I run 2WD most of the winter and don't need tire chains or 4WD very much...

 

The only time you would welcome big tires if you had to travel muddy field like the local cattle ranchers. They do have wide tires on their truck to prevent them from sinking down in the mud. 

20 minutes ago, Marcus2000monster said:

Mpg matters a lot too me but I also don’t want skinny dumb looking tires lol

 

 

What the difference between a stock 265's and a 235's...

 

1.1" narrower. 1mm taller. 25 pounds lighter. 2-3 MPG better. 

 

265's on the left and 235's on the right. If you didn't know the 235's are the stock size for the 1/2 ton and one ton trucks...

 

Just in my change from 256's to 235's I've extended my steering box live over 300k miles. I've only changed one set of ball joints and one track bar. Brakes last over 180k miles a set now. Shocks last well over 100k miles now and still going good.

 

Even my 1996 Ram 1500 is 235's and no issues with the front suspension at all. Compared to 285's and above most have suspension issues and steering issues. 

 

That's one of the reasons I traded in my 1972 Dodge Power Wagon is because I destroyed the front axle with over sized tires. 

 

Edited November 11, 2017 by Mopar1973Man

[trreed]

I had a set of 265/70/r17's on my truck over summer.  Yes there was less sidewall, but I did get better MPG's.  I recently went to a set of 285/70/r17's and while I like the look, I immediately noticed a severe mpg drop. (First thing I did with the new tires was drive the 264 mile loop I had driven all summer with the 265's.  Didn't even get halfway there before I knew mpgs were down.)  Best i've gotten with the 285's so far is 17.6 and that was a lot of coasting down mountains.  

Here's the look of the 265's.  I got used to the truck being a little lower.

Edited November 11, 2017 by trreed

[Dieselfuture]

How much does speedo get affected going from 235 to 285

[Mopar1973Man]

Since I know the 16 sizes well...

[Marcus2000monster]

I actually have 16 inch wheels by the way! 

Currently have 285/75/r16s right now. 

Based off of that what would you guys go with? Same size? I have no clue what these are as far as 32s 34s etc. Anyone know what they would be??

[jlbayes]

On 11/10/2017 at 9:15 PM, Dieselfuture said:

How much does speedo get affected going from 235 to 285

 

That is only the section width.

[trreed]

48 minutes ago, Marcus2000monster said:

I actually have 16 inch wheels by the way! 

Currently have 285/75/r16s right now. 

Based off of that what would you guys go with? Same size? I have no clue what these are as far as 32s 34s etc. Anyone know what they would be??

IIRC those are just under 33" diameter.  Still a big, heavy tire.

[CTcummins24V]

 What gear ratio do you have?  3.55s or 4.10s?

[Marcus2000monster]

4:10s

[CTcummins24V]

Hmm 285s(33s) rev too much with 4.10s? That should put your gear ratio around 3.73.

 

i would think 33s would be optimal. 

[Mopar1973Man]

14 minutes ago, CTcummins24V said:

Hmm 285s(33s) rev too much with 4.10s? That should put your gear ratio around 3.73.

 

i would think 33s would be optimal. 

 

Yeah but you missing half of the science. Now you've increased your rolling resistance and rotational mass. Rolling resistance increase with the larger contact patch of wider tires also the more the tread becomes aggressive the more this will increase as well. Rotational mass just the pure weight of the tire and wheel will add to this. So as you look at true racing the tires are always racing slicks being smooth tire face has the LEAST amount of rolling resistance also notice the front tire are typically super narrow to reduce more rolling resistance. Then all racing slicks typically are in the 20-30 pound range this is to keep rotational mass down and acceleration is much faster.

 

 

This all turn into efficiency. I know we can't run racing slicks on the street and have a traction tire for road condtions and weather conditions. What I'm trying to get at is don't fall into the "Gotta Look Cool" group that mounts on oversized tires then whines about front suspension failures and MPG just fell in the toilet. Consider what your doing and do you really need the wider tires for floatation for crossing muddy fields and true offroad travel.

 

Edited November 15, 2017 by Mopar1973Man

[Sycostang67]

My truck had the stock 265's when I got it , 18mpg.  I went with 285/75R16's and down to 16mpg.  Installing my Edge got me up to 19mpg, but then I got some 295/70R17's and went back down to 17mpg.  The one thing I will say about my 295's is my steering got easier.  These tires are either narrower or the large tread gaps(mud terrains) are reducing the friction and I haven't had a single stiff steering issue since I got them.  Doing the 3rd gen brake upgrade also made the truck stop like it had stock tires again. 

[Mopar1973Man]

295mm wide, 70% is height... So your 30mm wider then stock. 206.5 mm tall from the wheel.

 

265mm wide, 75% height or 198.75mm. so as you can see your a bit taller but much wider.

[Sycostang67]

You know the numbers , must just be the large tread gaps then.  Every time I had to tightly maneuver in a parking lot with the 285's(Toyo AT's) I would hit that point where the power steering felt like it wasn't working at all.  That hasn't happened with the 295's, just the occasional rubbing of the control arms. 

[Killer223]

that's because you are applying the weight over a wider area, so each contact has less psi down force on it than a narrow tire.

Edited November 17, 2017 by Killer223

[Mopar1973Man]

3 hours ago, Killer223 said:

that's because you are applying the weight over a wider area, so each contact has less psi down force on it than a narrow tire.

 

I should have a horrid time steering? Nope. 235/85 R16...

 

235/85 R16 (235mm / 199.75mm) (9.25" / 7.86") - 31.72" tall

265/75 R16 (265mm / 198.75mm) (10.43" / 7.82") - 31.64" tall

295/70 R17 (295mm / 206.5mm) (11.61" / 8.12") -  33.24" tall

 

Could have a lot to do with your tire pressure in the front axle. I run 60 PSI in the front and 40 PSI in the rear. I'm basing my tire pressure on axle weight. I've bolded the stock tire size and you can see the difference in metric and inches both.

 

I'vee just scaled my truck 3 days ago... My 235's are rated for 3,042 pounds at 80 PSI.

 

Front Axle (4,480 / 2) = 2,240 / 3,042 = 0.73 x 80 = 58.90 PSI

Rear Axle (2,980 / 2) = 1,490 / 3042 = 0.48 x 80 = 39.18 PSI

Edited November 17, 2017 by Mopar1973Man